1. Field of the Invention
The present invention relates to a method of manufacturing a V-pulley employed for a V-belt to transmit rotational power. More specifically, it relates to a press molding method for forming a pair of belt guides at the outer periphery of such a pulley to control both sides of a poly V-belt and a poly V-pulley having a multi-stage V-groove between the belt guides.
2. Description of the Related Art
Japanese Patent Laid-Open Publication No. Sho. 56-7775 discloses a conventional method of manufacturing a V-belt pulley, i.e., so-called a V-pulley, where disc-shaped metal material is first pressed to form a double cylindrically-shaped pulley material, and secondly a pair of belt guides is molded at the outer periphery of the pulley material for regulating both sides of the V-belt.
However, when the disc-shaped metal material has an uneven thickness, it causes excessive or lack of volume in the inner and the outer cylindrical portions of the double cylindrically-shaped pulley material, which means the inner and the outer cylindrical portions cannot be accurately formed into desired cylindrical shapes when those portions are molded. In this case, when the edge surface of the outer cylindrical portion is slotted to mold a belt guide in the subsequent process, the diameter of the belt guide fluctuates and the outline of the belt guide cannot be formed into a complete circle. Consequently, the V-pulley has eccentricity caused by imbalanced and uneven thickness, so that a rotor including the V-pulley irregularly rotates, which causes a shorter life of the bearing of the rotor and abnormal abrasion of the rotor.